The disclosed embodiments relate to a medical device. Specifically, the disclosed embodiments relate to a balloon catheter to be inserted into a target site (such as a stenosis site) in a blood vessel in order to expand the target site.
Balloon catheters for expanding stenosis sites and the like have already been proposed. A balloon catheter mainly comprises a balloon as an inflatable body; an outer shaft joined to a proximal end of the balloon; and an inner shaft inserted into the inside of the balloon and the outer shaft. In the conventional balloon catheter, the balloon can be detached from the inner shaft or the outer shaft at a joining portion therebetween when the balloon is inflated. Various configurations have been proposed in order to solve this problem.
For example, U.S. Pat. No. 6,918,920 discloses a balloon catheter in which a distal tip is joined to a distal end of an inner tube; a proximal shaft portion of a balloon is joined to the inner tube; and the inner tube, the distal tip, and the proximal shaft portion of the balloon are joined by a sleeve.
Further, Japanese Patent Application Laid-Open No. 2009-056297 discloses a balloon catheter in which a proximal end of a balloon is sandwiched between a tube body and a heat-shrinkable tube.
However, in the foregoing balloon catheter according to U.S. Pat. No. 6,918,920, the proximal shaft portion of the balloon is merely joined to an outer periphery of the inner tube. Therefore, the balloon tends to detach from the inner tube when the balloon is inflated. Further, although the distal tip is joined to the distal end of the inner tube and an inner periphery of the sleeve, the joining strength is not enough. Therefore, disadvantageously, the distal tip also tends to break off from the inner tube. Specifically, when the internal pressure is increased in order to inflate the balloon, the proximal shaft portion of the balloon becomes susceptible to detachment from the inner tube. When the internal pressure is further increased, the balloon and the inner tube are forced to extend in the distal direction. This causes the sleeve to be pushed from the proximal end, which, in turn, makes the sleeve susceptible to detachment, and the distal tip may break off from the inner tube.
Furthermore, even if the foregoing heat-shrinkable tube disclosed in Japanese Patent Application Laid-Open No. 2009-056297 were used instead of the foregoing sleeve in U.S. Pat. No. 6,918,920, the distal tip might nonetheless break off from the inner shaft.